Superficial gyp changes to not immediately error out on Windows

tools/tools.gyp

Index: tools/tools.gyp
diff --git a/tools/tools.gyp b/tools/tools.gyp
index 344d4034a6d7dc1ef405c32e384491d755096ba0..22f6fc582d13c59b115fea244ab106d48eead65c 100644
--- a/tools/tools.gyp
+++ b/tools/tools.gyp
@@ -72,12 +72,16 @@
       'include_dirs': [
         '..',
       ],
-      'link_settings': {
-        'libraries': [
-          '$(SDKROOT)/System/Library/Frameworks/CoreFoundation.framework',
-          '$(SDKROOT)/System/Library/Frameworks/Foundation.framework',
-        ],
-      },
+      'conditions': [

[Mark Mentovai, 2014/09/30 19:55:01]

None of these tools make any sense off of Mac. We should just move all three
tools into a Mac-only condition.

[scottmg, 2014/09/30 19:59:49]

Done.

+        ['OS=="mac"', {
+          'link_settings': {
+            'libraries': [
+              '$(SDKROOT)/System/Library/Frameworks/CoreFoundation.framework',
+              '$(SDKROOT)/System/Library/Frameworks/Foundation.framework',
+            ],
+          },
+        }],
+      ],
       'sources': [
         'on_demand_service_tool.mm',
       ],